﻿<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>微信授权登陆</title>
</head>
<body>
    <script>
        var GWC = {
            urlParams: {},
            appendParams: function (url, params) {
                if (params) {
                    var baseWithSearch = url.split('#')[0];
                    var hash = url.split('#')[1];
                    for (var key in params) {
                        var attrValue = params[key];
                        if (attrValue !== undefined) {
                            var newParam = key + "=" + attrValue;
                            if (baseWithSearch.indexOf('?') > 0) {
                                var oldParamReg = new RegExp(key + '=[-%.!~*\'\(\)\\w]*', 'g');

                                if (oldParamReg.test(baseWithSearch)) {
                                    baseWithSearch = baseWithSearch.replace(oldParamReg, newParam);
                                } else {
                                    baseWithSearch += "&" + newParam;
                                }
                            } else {
                                baseWithSearch += "?" + newParam;
                            }
                        }
                    }

                    if (hash) {
                        url = baseWithSearch + '#' + hash;
                    } else {
                        url = baseWithSearch;
                    }
                }
                return url;
            },
            getUrlParams: function () {
                var pairs = location.search.substring(1).split('&');
                for (var i = 0; i < pairs.length; i++) {
                    var pos = pairs[i].indexOf('=');
                    if (pos === -1) {
                        continue;
                    }
                    GWC.urlParams[pairs[i].substring(0, pos)] = decodeURIComponent(pairs[i].substring(pos + 1));
                }
            },
            doRedirect: function () {
                var code = GWC.urlParams['code'];
                var appId = GWC.urlParams['appid'];
                var scope = GWC.urlParams['scope'] || 'snsapi_base';
                var state = GWC.urlParams['state'];
                var redirectUri;

                if (!code) {
                    //第一步，没有拿到code，跳转至微信授权页面获取code
                    redirectUri = GWC.appendParams('https://open.weixin.qq.com/connect/oauth2/authorize#wechat_redirect', {
                        'appid': appId,
                        'redirect_uri': encodeURIComponent(location.href),
                        'response_type': 'code',
                        'scope': scope,
                        'state': state,
                    });
                } else {
                    //第二步，从微信授权页面跳转回来，已经获取到了code，再次跳转到实际所需页面
                    redirectUri = GWC.appendParams(GWC.urlParams['redirect_uri'], {
                        'code': code,
                        'state': state
                    });
                }

                location.href = redirectUri;
            }
        };

        GWC.getUrlParams();
        GWC.doRedirect();
    </script>
</body>           
</html>